1. Field of the Invention
The present invention relates to an insertion instrument and an endoscope that has an elongated insertion portion that is inserted into a subject, and a bendable bending portion that is provided in the insertion portion and that bends accompanying pulling/relaxing of a wire that is passed through the insertion portion.
2. Description of the Related Art
In recent years, an insertion instrument, for example, an endoscope, that is inserted inside a subject or an object is being widely used in a medical field and an industrial field. An endoscope used in the medical field observes an organ inside a body cavity of a subject by inserting an elongated insertion portion into the body cavity. As necessary, the endoscope can perform various kinds of treatment using a treatment instrument that is inserted inside a treatment instrument insertion channel provided in the endoscope.
Further, with an endoscope used in the industrial field, by inserting an elongated insertion portion of the endoscope inside an object such as a jet engine or pipes of a factory, it is possible to conduct an observation to check for the presence of flaws or corrosion or the like at a site to be examined inside the object and to perform various kind of repairs.
A configuration is known in which a bending portion that is bendable in a plurality of directions is provided in an insertion portion of an endoscope. The bending portion improves the advancing ability of the insertion portion at a curved section inside a duct, and also varies an observation direction of an observation optical system provided in a distal end portion that is positioned further on a distal end side in the insertion direction (hereunder, referred to simply as “distal end side”) than the bending portion in the insertion portion.
Normally, a bending portion provided in an insertion portion of an endoscope is configured to be bendable in, for example, four directions, namely, upward, downward, left, and right, by connecting a plurality of bending pieces along the insertion direction of the insertion portion.
Further, the bending portion is configured to be bendable in any of the upward, downward, left, and right directions by performing a pulling operation from an operation portion with respect to any of four wires that are passed through the inside of the insertion portion and whose distal ends are fixed to a bending piece that is positioned furthest on the distal end side among the bending pieces.
In this connection, the reason that only the bending portion bends accompanying an operation to pull a wire is that, in the insertion portion, an outer circumference of the wire that is inside a flexible tube portion which exhibits flexibility that is positioned further on a proximal end side in the insertion direction (hereunder, referred to simply as “proximal end side”) than the bending portion is covered by a coil pipe or the like in a state in which a distal end and a proximal end thereof in the insertion direction are fixed inside the flexible tube portion. Another reason is that, even if a wire is pulled, the coil pipe resists a compressive force that is applied to the coil pipe along an extending direction of the coil pipe.
In this connection, a bending portion that has a short length in the insertion direction, that is, a bending portion with a small bending radius, is capable of small adjustments. Hence, such a bending portion is advantageous because the ability of the distal end portion of the insertion portion to pass through a curved section inside a duct is enhanced thereby, and an observation optical system provided in the distal end portion can be easily brought close to a site to be examined.
This is because, when a bending portion has a long length, for example, if the endoscope in question is a medical endoscope, when the endoscope is inserted into the colon, at a curved section of the colon the distal end portion is liable to contact the curved section and the field of view will be lost. More specifically, when a short bending portion is used, the distal end portion is not liable to contact against an intestinal wall at a curved section. Note that the number of connected bending pieces may be decreased to shorten the length of the bending portion.
Further, with a medical endoscope, a technique is commonly used in which, after the distal end portion passes through a curved section, the curved section is straightened by drawing in the proximal end side of the insertion portion in a state in which the distal end portion and the bending portion are hooked to tissue inside the body cavity, and thereafter the bending portion is caused to pass through the curved section by pushing in the insertion portion from the proximal end side.
Japanese Patent Application Laid-Open Publication No. 10-248794 discloses a configuration and technique that enhance the insertability of an insertion portion into the colon by first inserting a known overtube into a body cavity, and thereafter inserting the insertion portion into the overtube.
In addition, Japanese Patent Application Laid-Open Publication No. 2008-253774 discloses a configuration in which a first bending portion and a second bending portion are provided as two bending portions on a distal end side of an insertion portion. More specifically, the second bending portion is formed with a more rigid configuration than the first bending portion at a position that is further on the proximal end side than the first bending portion.
Furthermore, Japanese Patent Application Laid-Open Publication No. 2005-185526 discloses a configuration in which two shape memory alloys whose rigidity increases accompanying the supply of a current thereto are provided along the insertion direction inside a bending portion that is positioned on a distal end side of an insertion portion.
Japanese Patent Application Laid-Open Publication No. 10-248794 also discloses a configuration that avoids the occurrence of a sticking phenomenon by decreasing friction with the colon by causing an insertion portion to vibrate using a vibration unit.